package aaa0proxy;

public class MD5 {
	/*
	 * 四个链接变量
	 */
	private final int A = 0x67452301;
	private final int B = 0xefcdab89;
	private final int C = 0x98badcfe;
	private final int D = 0x10325476;
	/*
	 * ABCD的临时变量
	 */
	private int Atemp, Btemp, Ctemp, Dtemp;

	/*
	 * 常量ti公式:floor(abs(sin(i+1))×(2pow32)
	 */
	private final int K[] = { 0xd76aa478, 0xe8c7b756, 0x242070db, 0xc1bdceee,
			0xf57c0faf, 0x4787c62a, 0xa8304613, 0xfd469501, 0x698098d8,
			0x8b44f7af, 0xffff5bb1, 0x895cd7be, 0x6b901122, 0xfd987193,
			0xa679438e, 0x49b40821, 0xf61e2562, 0xc040b340, 0x265e5a51,
			0xe9b6c7aa, 0xd62f105d, 0x02441453, 0xd8a1e681, 0xe7d3fbc8,
			0x21e1cde6, 0xc33707d6, 0xf4d50d87, 0x455a14ed, 0xa9e3e905,
			0xfcefa3f8, 0x676f02d9, 0x8d2a4c8a, 0xfffa3942, 0x8771f681,
			0x6d9d6122, 0xfde5380c, 0xa4beea44, 0x4bdecfa9, 0xf6bb4b60,
			0xbebfbc70, 0x289b7ec6, 0xeaa127fa, 0xd4ef3085, 0x04881d05,
			0xd9d4d039, 0xe6db99e5, 0x1fa27cf8, 0xc4ac5665, 0xf4292244,
			0x432aff97, 0xab9423a7, 0xfc93a039, 0x655b59c3, 0x8f0ccc92,
			0xffeff47d, 0x85845dd1, 0x6fa87e4f, 0xfe2ce6e0, 0xa3014314,
			0x4e0811a1, 0xf7537e82, 0xbd3af235, 0x2ad7d2bb, 0xeb86d391 };
	/*
	 * 向左位移数,计算方法未知
	 */
	private final int s[] = { 7, 12, 17, 22, 7, 12, 17, 22, 7, 12, 17, 22, 7,
			12, 17, 22, 5, 9, 14, 20, 5, 9, 14, 20, 5, 9, 14, 20, 5, 9, 14, 20,
			4, 11, 16, 23, 4, 11, 16, 23, 4, 11, 16, 23, 4, 11, 16, 23, 6, 10,
			15, 21, 6, 10, 15, 21, 6, 10, 15, 21, 6, 10, 15, 21 };

	/*
	 * 初始化函数
	 */
	private void init() {
		Atemp = A;
		Btemp = B;
		Ctemp = C;
		Dtemp = D;
	}

	/*
	 * 移动一定位数
	 */
	private int shift(int a, int s) {
		return (a << s) | (a >>> (32 - s));// 右移的时候，高位一定要补零，而不是补充符号位
	}

	/*
	 * 主循环  512bit 16group
	 */
	private void MainLoop(int group[]) {
		int F, g;
		int a = Atemp;
		int b = Btemp;
		int c = Ctemp;
		int d = Dtemp;
		//主循环有四轮， 每一轮由16次操作组成。F、G、H、I函数   每一轮应用一个函数
		/* 一共4轮，每一轮使用不同函数*/  
		for (int i = 0; i < 64; i++) {
			if (i < 16) {
				F = (b & c) | ((~b) & d);
				g = i;
			} else if (i < 32) {
				F = (d & b) | ((~d) & c);
				g = (5 * i + 1) % 16;      //1  6   11  0 5 10  15  4  9
			} else if (i < 48) {
				F = b ^ c ^ d;
				g = (3 * i + 5) % 16;
			} else {
				F = c ^ (b | (~d));
				g = (7 * i) % 16;
			}
			int tmp = d;
			d = c;
			c = b;
			int mov_bits_count = s[i];
			b = b + shift(a + F + K[i] + group[g], mov_bits_count);
			a = tmp;
		}
		//、、将A、B、C、D分别加上AA、BB、CC、DD，然后用下一块数据继续进行算法。
		Atemp = a + Atemp;
		Btemp = b + Btemp;
		Ctemp = c + Ctemp;
		Dtemp = d + Dtemp;

	}

	/*
	 * 填充函数处理后应满足bits≡448(mod512),字节就是bytes≡56（mode64)填充方式为先加一个0,其它位补零
	 * 最后加上64位的原来长度
	 */
	private int[] padding(String str) {
		int num = ((str.length() + 8) / 64) + 1;// 以512位，64个字节为一组
		int strByte[] = new int[num * 16];// 64/4=16，所以有16个整数
		for (int i = 0; i < num * 16; i++) {// 全部初始化0
			strByte[i] = 0;
		}
		int i;
		for (i = 0; i < str.length(); i++) {
			strByte[i >> 2] |= str.charAt(i) << ((i % 4) * 8);// 一个整数存储四个字节，小端序
		}
		strByte[i >> 2] |= 0x80 << ((i % 4) * 8);// 尾部添加1
		/*
		 * 添加原长度，长度指位的长度，所以要乘8，然后是小端序，所以放在倒数第二个,这里长度只用了32位
		 */
		strByte[num * 16 - 2] = str.length() * 8;
		return strByte;   //===32arr*4byte=    liage* 512bit(64byte)
		//===16arr *4===64byte
	}

	/*
	 * 调用函数
	 */
	public String getMD5(String source) {
		init();
		int strByte[] = padding(source);  //leng=32
		int splitBy16count = strByte.length / 16;
		for (int i = 0; i < splitBy16count; i++) {
			int num[] = new int[16];
			for (int j = 0; j < 16; j++) {
				num[j] = strByte[i * 16 + j];
			}
			MainLoop(num);
		}
		return changeHex(Atemp) + changeHex(Btemp) + changeHex(Ctemp)
				+ changeHex(Dtemp);

	}

	/*
	 * 整数变成16进制字符串
	 */
	private String changeHex(int a) {
		String str = "";
		for (int i = 0; i < 4; i++) {
			str += String.format("%2s",
					Integer.toHexString(((a >> i * 8) % (1 << 8)) & 0xff))
					.replace(' ', '0');

		}
		return str;
	}

	/*
	 * 单例
	 */
	private static MD5 instance;

	public static MD5 getInstance() {
		if (instance == null) {
			instance = new MD5();
		}
		return instance;
	}

	private MD5() {
	};

	public static void main(String[] args) {
		// 603f52d844017e83ca267751fee5b61b
 	String str = MD5.getInstance().getMD5("jklmn");// 603f52d844017e83ca267751fee5b61b
 	System.out.println(str);
		System.out.println(MD5.getInstance().getMD5("attilaxattilaxattilaxattilaxattilaxattilaxattilaxattilax"));//56byte
		//c4e10de24d19bc837fc5b0f8a5169343
	}
}